Nano-Hydroxyapatite Gel and Its Effects on Remineralization of Artificial Carious Lesions

Published In: International Journal of Dentistry
Publication Year: 2021

Study Design

This was an in vitro randomized controlled study comparing the remineralization effects of nano-hydroxyapatite in gel and toothpaste form against fluoride varnish and an untreated control group.

Funding Sources

The study was supported by the Faculty of Dentistry, Khon Kaen University (KKU) and the Ministry of Higher Education, Science, Research and Innovation, RTG (Thailand).

PICO Framework – What Was Studied and How?

Population:
Extracted human bicuspids (n=100), caries-free, used to simulate artificial carious lesions.

Intervention:
Application of nano-hydroxyapatite gel (20% NHG and 30% NHG).

Comparison:
Nano-hydroxyapatite toothpaste (NHT), fluoride varnish (FV), and no treatment (NT).

Outcomes:

• Surface microhardness recovery (%HR)

• Depth of lesion reduction (via polarized light microscopy)

• Crystal structure changes (X-ray diffraction)

In paragraph form:
This study used extracted human bicuspids with artificially created enamel caries to compare the remineralization capabilities of nano-hydroxyapatite gel at 20% and 30% concentrations against a nano-hydroxyapatite toothpaste, fluoride varnish, and no treatment. The primary outcomes were enamel surface microhardness recovery and reduction in caries lesion depth.

Inclusion and Exclusion Criteria

Inclusion Criteria:

• Extracted human bicuspids free from caries, white spots, or enamel cracks.

Exclusion Criteria:

• Teeth with visible caries or enamel structural abnormalities.

Demographics and Study Groups

Total Samples: 100 teeth (sectioned into enamel specimens)
Group Size: 20 per group

• FV (Fluoride varnish): 20 specimens

• NHT (Nano-hydroxyapatite toothpaste): 20 specimens

• 20% NHG: 20 specimens

• 30% NHG: 20 specimens

• NT (No treatment): 20 specimens

Primary Outcome Variables and Results

Outcome: Vickers Surface Microhardness Recovery (%HR)

Hardness Difference (HA - HD):

• NHT: 38.00 ± 10.33

• 20% NHG: 27.72 ± 7.99

• 30% NHG: 26.33 ± 7.64

• FV: 10.77 ± 7.80

• NT: 1.50 ± 10.22

Conclusions

• Nano-hydroxyapatite gel at both 20% and 30% concentrations significantly remineralized enamel lesions, improving hardness and reducing lesion depth.

• Nano-HA toothpaste showed the highest remineralization potential among all agents tested.

• Nano-HA gels performed better than fluoride varnish, suggesting a promising non-invasive alternative for enamel repair.

Discussion: Strengths and Limitations

Strengths

• Rigorous experimental design with controlled conditions.

• Use of multiple analytical tools (Vickers hardness testing, SEM, PLM, XRD) for robust assessment.

• Compared two concentrations of NHG, offering insight into dosage effects.

Limitations

• In vitro model: Clinical behavior may differ in the oral environment.

• Short treatment duration: Long-term effects were not assessed.

• No biological variables (e.g., saliva, bacterial biofilm) included.

Additional Insights:

• Increasing NHG concentration from 20% to 30% did not significantly enhance outcomes, likely due to saturation effects or particle aggregation.

• Toothpaste form (NHT) had a slightly acidic pH (5.83), which may have enhanced mineral penetration compared to alkaline NHG gels (pH ~9.5–9.8).

Citation

Juntavee A, Juntavee N, Sinagpulo AN. Nano-hydroxyapatite gel and its effects on remineralization of artificial carious lesions. Int J Dent. 2021;2021:7256056. doi:10.1155/2021/7256056
📖 PubMed Link 

Visual Aids

Chart: Enamel Surface Hardness Recovery